Apparatus for and method of gapping spark plugs



E. MOSTHAF Sept. 17, 1940.

APPARATUS FOR AND METHOD OF GAPPING SPARK PLUGS Filed Oct. 19, 193 3Sheets-Sheet 1 INVENTOR EDWIN M057'HAF BY TIORNEY 1937 a Sheets-Sheet 2I I I I 55 i I I I I I l I I l I I I l I I I I l INVENTOR EDWIN OSTHAFyfly/ TI'ORNEY E. MOSTHAF APPARATUS FOR AND METHOD OF GAPPING sum rulesFiled Oct. 19

Sept. 17, 1940.

54 fig; 3

I Fig. 4

Sept. 17, 1940. E. MOSTHAF 2,215,333

APPARATUS FOR AND METHOD GAPPING SPARK PLU GS Filed Oct. 19, 3.93 3Sheets-Sheet 3 ii lll flTlll 54 INVENTOR AEDWIN STHAF F 7 BY q' ATTORNEYPatented Sept. 17, 1940 UNITED STATES TsNr APPARATUS FOR AND METHOD OFGAPPING SPARK PLUGS This invention relates to spark plugs, moreparticularly to the method of obtaining absolute uniformity in the gapsduring mass production of the spark plugs.

In the past, the gaps of spark plugs have been formed by the use ofmanual tools and gauges. This process is expensive due to the time andcare required on the part of the operator setting the gap, and, at thesame time, is inefficient due to the error of the personal equation ofthe operator. With the limits of tolerance required in the usualmanufacturing processes, the average operator had many rejects whichwere unacceptable as varying too far from the standard. The return ofthe rejects caused the cost of manufacturing to increase. Although themanual setting of gaps is very unsatisfactory and costly, it has beenused in most of the spark plug manufacturing processes.

Electrical means have also been devised for this purpose which employ aphoto-electric cell to control the oscillations of a magnetic hammer tobend the side electrodes of the spark plug by a quick succession ofblows into proper relation with the center. The photo-electrictube wasemployed to control the length of the gap by stopping the blows of thehammer when the gap reached the required size. Although this systemformed the gaps with a high degree of accuracy, it was found difficultto maintain the means in operation under average conditions in themanufacturing plant, the photo-electric cell being a very sensitivedevice and subject to frequent break-down.

Mechanical means havealso been devised to gap the electrodes of thespark plug which have been found altogether unsatisfactory because thegaps formed on a long series of plugs could not be maintained withindesired manufacturing tolerances. t

The present invention contemplates the provision of a method of-gappingthe electrodes of a spark plug in which substantial uniformity of gapsmay be maintained, and in which the stresses arising in the conformationof the electrodes are localized to a minimum section, the method beingsuitable for mass production in a manufacturing plant. At the same time,the speed with which the gaps can be set is sufficiently high tomaintain the production costs at a minimum. The invention. furthercontemplates the design of a machine incorporating the method which canbe operated by a man of average intelligence and thereby allows the useof unskilled labor in the fabrication of the spark plug.

It is, therefore, an object of this invention to' provide a method offorming gaps for the electrodes of the spark plug with absoluteuniformity and with a speed sufficient to maintainthe production costsof the spark plug at a minimum.

It is a further object of this invention to provide a method to gap theelectrodes of a spark plug in which the initiating point from'which thelength of the gap is measured is a point on one of the electrodes whichwill give absolute uniformity of gap by the use of a template formeasuring the length of gap.

It is a further object of this invention to provide a method of gappingspark plugs in which the bending stresses arising in the conformation ofthe electrodes will be localized in a minimum section so that relaxationof the conformed section of the electrode under operating conditions ofhigh temperature will not substantially vary the gap dimension.

It is a further object of this invention to provide a machine which willallow the contour of the electrodes to be changed to a desirable designwithout interfering with the accuracy of the gap-setting process.

Other objects and advantages of this invention relating to thearrangement, operation and function of the related elements of thestructure, to Various details of construction, to combinations of partsand to economics of manufacture, will be apparent to those skilled inthe art upon consideration of the following description and appendedclaims, reference being had to the accompanying drawings forming a partof this specification wherein like reference characters designatecorresponding parts in the several views.

Figure 1 is a plan view, partly in section, incorporating the invention.

Figure 2 is an elevational View, partly in section, taken along the line2-2 of Figure 1.

Figure 3 is an enlarged plan View, taken along the line 3-3 of Figure 2.

Figure 4 is an enlarged view, taken along the line 4-4 of Figure 2.

Figures 5, 6 and '7 are an elevational moving picture, taken along theline 55 of Figure 1.

Referring to the drawings, particularly to Figures 1 and 2, a supportingstructure is supplied for a machine incorporating a modification of theinvention which consists essentially of a base member ID having twoupright plates IDA and IDB connected integrally together by means ofwebs IDC and IDD which hold the plates in spaced relation. The uprightplates IDA and |DB are provided with flanges at their bottoms to providea convenient means for mounting the structure upon a table or the like.Forwardly of the web IDD, a jutting portion II is provided which isadapted to support mechanisms to be described hereinafter.

Adjacent the upper end of the upright plates IDA and IDB, a closureplate I2 is provided which is held in position upon the upright platesIDA and IDB by means of stud bolts I3 which are threaded into alignedopenings in the upright plates. The space between the upright plates [DAand IDB is provided with a sliding block I4 which is adapted to move ina horizontal direction between the upright plates and is held inposition therebetween the plate I2 and the ledge I5 but on the innersides of the upright plates. A lack I6 is attached to-the lower edge ofthe sliding block I4 by being fitted into a slot in the block and heldin position by means of stud bolts l'I. Cooperating with the rack I6,pinion I8 is provided which is mounted upon a jack shaft I9 suitablyjournaled in proper hearings in the upright plates IDA and IDB. The jackshaft I9, adjacent one of its outer ends, is provided with a bell-crankattached thereto by means of pin 2|. Adjacent the end of the bellcrank20, a bent rod 22 is provided to connect the bell-crank with a suitablemanual means (not shown) such as a foot lever.

By this structure, the movements of the sliding block M are undercontrol of a foot lever which allows the block I4 to advance forwardlyand to return at the will of an operator. The forward movement of thesliding block I4 is limited by a stud 23, upon which are positioned locknuts 24 to allow adjustment of the forward movement of the sliding blockM. The stud 23 co bperat'es with an aperture in a plate which is held inposition on the upright plates IDA and 'IDB by means of stud bolts 26,the plate 25 acting as a stop for the lock nuts 24 to limit the movementof the sliding block. The rearward movement of the sliding block iscontrolled by the cooperation of the rear face of the sliding block I4and the plate 25 as shown in Figure 2. 4 Upon the forward face of thesliding block I4, a projection |4A is provided, upon which'is positioneda bracket 38 by means of stud bolt 3| positi'oned on the verticalportion of the bracket 30. A bifurcated portion 32 on the bracketsupports the journal'shaft 33 of a roller 34. An adjustment is providedto control the vertical displacement of the roller 34 comprising anadjustment screw 35 cooperating with the horizontal portion of thebracket 30 and a slot 36 in the vertical portion cooperating with thestud bolt 3|. The movement of the sliding block I4 forwardly advancesthe notched roller 34 in a horizontal direction with reference to atemplate 40 held in spaced relation with the roller by means 'of abracket 4|, which is preferably attached to the projection II of thebase by means of stud bolts 42 (Figure 1). The template 4D is attachedto the bracket 4| by means of screws 43 whose heads are preferablycounter-sunk to be flush with theltop surface of the template.

, The template 4D is more clearly shown in Figure 3. A notch 44 isprovided on the edge of the template opposite the screws 43 and channel45 is cut on the lower side of the template in spaced relation with thenotch 44, the distance between the channel and the notch being dependentupon the size of the spark plug which is to be manufactured. The notch44 is designed to cooperate with the unbent side electrodes as shown inFigure 5, while the-channel, which is parallel thereto, is designed tocooperate with the end of the center electrode C of a spark plug D. Thewidth of the notch 44 and channel 45 is dependent upon the diameter ofthe electrodes of the spark plug; the length of the channel and notch,as measured from the vertical or narrow side of the template, is suchthat the center of the roller 34 which is provided with a peripheralnotch 34A traverses a plane passing through the centers of both the sideelectrode and the center electrode in its lateral movement under theinfluence of the sliding block l4.

The side of the notch 44 adjacent the channel 45 is preferably providedwith a chamfer 44A, so that the side wire will be bent in the form of asmooth curve rather than a sharp angle. the case in which the side wireis given a peculiar conformation, such as shown in Figure 5, it ispreferable to conform the upper surface of the template 4D to conform tothe shape of the side wire. This is clearly shown in Figure 5, in whichthe template 4B is provided with a slightly raised portion 40A, so thatit will fit, in the case illustrated, with the indentation on the sidewire.

The channel 45, as pointed out before, does not pierce the template 40but extends into it for a definite distance to provide a wall 45A ofpredetermined thickness between the bottom of the channel 45 and the topsurface of the template 4!). The thickness of the wall 45A determinesthe size of the gap which will be formed between the side and the centerelectrode of the spark plug after the gapping operation is complete.This operation will be described in further detail hereinafter. 4

In order to hold the spark plug inproper position during the process ofgapping to obtain the greatest possible uniformity of gap, and at thesame timeassure convenience in positioning the spark plug in operablerelation in the machine, and removing it after the operation iscomplete, a novel structure is provided which will accomplish' thesepurposes. prises generally of two interdependent structures, the firstof which operates upon the threaded shank of the spark plug so as toprevent a lateral movement of the electrodes as the plug is held inoperable position in'the notch 44 and the channel 45; and the secondholds the plug in operative relation with the template 40 by placing aforce upon the plug in a longitudinal direction; that is, thrusting onthe tip of the insulator to push the center electrode into closecontactual relation with the wall 45A at the bottom of the channel 45.Through the agency of these two structures, the plug is securely held inposition to prevent both lateral and longitudinal movement, so thattheroller 34 may operate most effeotually.

The first structure mentioned, which prevents the lateral movement ofthe plug, comprises a hemispherical notch upon the forward edge of thebracket 4| immediately below the template 4D, the notch being of thediametrical dimension of the threaded shank of the spark plug to befitted therein. To hold the shank of the plug in The holding meanscorndirection against the action of a resilient means 5'! whichfunctions between a pin 51A on the bell-crank and an anchor pin 58 onthe bracket 41. The bell-crank 54 is locked to the spindle 55 by meansof pin 59, the spindle being journaled in proper bearings 60 within abore in the bracket 4|.

On the lower end of the spindle 55, a cam member 62 is locked to thespindle by means of a pin 63, so that the movement of the cam member isunder the control of the manual handle means 56. The cam member 62cooperates with a cam button 54, positioned on a lever 55 whose one endis pivoted about a pin 66 for rotation thereabout. The pin 66 is held inposition by means of a biiurcated bracket 6'! which is adjustablypositioned by means of screws 68 adjacent the bottom of the bracket 4|.The opposite end of the lever 65 extends through a slot 70 into avertical bore 1! in the projection H of the base member. A plunger 12 isprovided to reciprocate within the bore H under the influence of thelever 65 against the action of a resilient means 13, acting between ashoulder on the plunger 32, and a threaded plug 14, screwed into athreaded counter-bore 15 on the lower end of the bore H. Adjacent theslot H1 in the projection H, a flared slot 16 is provided in the plunger12 to cooperate with the end of the lever 65 projecting through the slot10. By this structure, the bell-crank 54 is enabled to thrust theplunger 12 downwardly by means of a cam member 62 and the pivoted lever65 against the action of the resilient means 13.

On the upper end of the plunger 12, an aperture I? is provided tocooperate with the head of the insulator of the spark plug to be gapped,so that a non-slip grip is obtained between the plunger 12 and the sparkplug. This enables the resilient means 73 to apply a longitudinal thrustto the spark plug to accomplish the purposes set out above.

From this structure, it is apparent that the holding means comprisingthe two structures which prevent lateral and longitudinal movement ofthe spark plug when it is in operable relation with the template 40, isunder the control of one manual means, viz; the manual lever 56. Whenthe manual lever 56 (Figure 1) is turned in a counter-clockwisedirection against the action of the resilient means 51 and 13, it movesthe lock ing block 5! from its contact with the threaded shank of thespark plug and simultaneously thrusts the plunger 12 downwardly by theaction of the cam member 62 on the cam button 64 to remove thelongitudinal thrust from the tip of the insulator. When the lever 56 isin its extreme counter-clockwise position, the plunger l2 will bedepressed and the locking member 5! will be removed to a considerabledistance from the initial position shown in" Figure l, which locks theplug securely in position for the application of the gapping method.

Referring to Figures 5, 6 and 7, the interaction between the template,the spark plug, and the roller is clearly illustrated. Figure 5illustrates the initial position in which the plug has been placed inoperable relation with regard tothe template, assuming that both holdingmeans are in operative position. At thistime, the operator actuates amanual means, for example, a foot lever acting on the bar 22 to thrustthe roller 34 means5'l and T3 willreturn the lever 56 to its forwardlyand bends the side electrode over the chamfered edge i iA of the slot 44into final position. This action is clearly illustrated in Figure 6. Theoperator continues depressing the manual means until roller 34 hascompletely passed the electrodes of the spark plug, as illustrated inFigure 7. At this time, he releases the manual means which returns theroller to its initial position either by resilient means or throughmanual operation. The parts of the machine are returned to the initialposition as shown in Figure 5 v with the exception that the sideelectrode has been bent into position over the center electrode with thewall 5511. which is ofpredetermined thickness to establish the propergap size between the electrodes. The operator then moves the manualmeans 56 in a counter-clockwise direction and removes the plug from itsoperable relation with the template All by moving it in a lateraldirection so as to disengage the side elecall trode and the centerelectrode from the notch 44 and the channel 45. He then places anungapped plug in position with regard to the template 563 and the cyclebegins again.

The formation of the gaps of spark plugs by this method givesgreaterruniiormity in the dimension of the gap-s and does not disturbthe other elements of the plug so as to break the seal between thecenter electrode and the insulator or the insulator and the shell. Theconcentration or localization of the bending stresses of the electrodesinto a small section, reduces the relaxation of the stressed metal to aminimum during the high temperatures to which it is subjected duringuse, the gap thereby remaining substantially the same until a stablecondition is attained in the electrode metal. Should the electrode metalbe especially difficult to conform, so that its resiliency will preventthe gap from being formed by the exact dimension of the template, anallowance can be made in the dimension of the template to compensate forthe springback.

It is to be understood that the above detailed description of thepresent invention is intended to disclose an embodiment thereof to thoseskilled in the art, but that the invention is not to be construed aslimited in its application to the details of construction andarrangement of parts illustrated in the accompanying drawings, since theinvention is capableof being practiced and carried out in various wayswithout departing from the spirit of the invention. The language used inthe specification relating to the operation and function of the elementsof the invention is employed for purposes of description and not oflimitation, and it is not intended to limit the scope of the followingclaims beyond the requirements of the prior art.

What is claimed:

1. In a device of the class described, a template having a channel tocooperate with the ;center wire of the spark plug, the dimension of;trode cooperating with the bottom of the channel,

and reciprocating roller means to bend the side electrode into operablerelation with the center electrode to place the template portion at thebottom of the channel between the electrodes.

2. In a device of the class described, a template having a slot toaccommodate the side electrode and a channel to accommodate the centerelectrode of the spark plug, means to hold the plug in operable positionwith the template with the end of the center electrode in the base ofthe channel, and means to bend the side electrode into operable relationwith the center electrode to place the template portion at the bottom ofthe channel between the end of the center electrode and the bent-overside electrode.

3. The method of gapping the electrodes of a spark plug, comprising,resiliently holding the center electrode of the plug against a template,locking the plug against lateral movement with respect to the templateand bending the side electrode into operable relation with the centerelectrode having the template between the electrodes to assure thedimension of the gap between the electrodes.

4. In a device of the class described, a template adapted to cooperatewith the center electrode of the spark plug, centering means tocooperate with the template and the spark plug to align the parts inproper operative relation, resilient holding means to thrust the centerelectrode against the template, a second holding means cooperating withthe centering means to prevent lateral movement of the spark plug, meansto bend the side electrode into operable relation with the centerelectrode, the gap between the side electrode and the center electrodebeing predetermined by the thickness of the template and manual means tocontrol the holding means and the means to bend the side electrode.

5. In a device of the class described, a template adapted to cooperatewith the center electrode of the spark plug and being of the samethickness as the length of the desired gap, resil ient holding means tothrust the center electrode into operable relation with the template, asecond holding means to prevent lateral movement of the spark plug,means to control both holding means, reciprocating means to bend theside electrode into operable relation with the center electrode over thetemplate, adapted to bend the electrode sharply in a minimumlongitudinal section,

the gap between the electrodes being determined by the thickness of thetemplate, and means to control the means to bend the side electrode.

6. The method of gapping a spark plug, comprising, completely assemblingthe spark plug with the electrodes in substantially parallel relation,positioning a template, having a predetermined thickness adjacent thecenter electrode to establish the dimension of the gap and a relativelysharp edge adjacent the side electrode, against the electrodes andthen'bending the side electrode over the relatively sharp edge of thetemplate to concentrate the area of the bend formed in the electrode andto place the side electrode a predetermined distance from the centerelectrode as determined by thickness of the template.

7. The method of gapping a spark plug, comprising, completely assemblingthe spark plug, positioning a template firmly in relation with theelectrodes, the template having a thickness of predetermined dimensionto establish the length of the gap, and an upper surface formed topredetermine the shape and location of the conformed area of the sideelectrode and bending the side electrode over the template by a rollermoving in a plane parallel to the upper surface of the template andsubstantially normal to the center electrode.

8. In a device of the class described, a template, means to hold a sparkplug adjacent the template with the center electrode touching thetemplate in substantially normal relation, and reciprocating means tobend a side electrode of the plug into cooperative relation with thecenter electrode, with the template positioned between them to determinethe length of the gap between the center electrode and the bent-overside electrode.

EDWIN MOSTHAF.

